There has been proposed an image display device which includes: an image display surface (liquid crystal display panel and the like) for displaying an image including a three-dimensional image; and an image transmission panel (image-forming optical element) provided on the near side (viewer side) of the image display surface in spaced apart relation to the display surface and for forming the aforementioned image (spatial image) in space (see PTL 1, for example).
This image display device is provided with a pair of microlens arrays (image-forming optical element) positioned in a parallel spaced-apart relation to the image display surface and including a plurality of convex lenses (unit optical elements) disposed adjacent to each other in a matrix on opposite surfaces. Using the image-forming function of the microlens arrays, the image display device is capable of projecting (forming) an erect image of unity magnification corresponding to the aforementioned image in a space opposite from the aforementioned display surface (in a position opposite from the display surface with respect to the element surface of the image-forming optical element).
There has been proposed another example in which a three-dimensional frame of an aquarium and the like containing water is disposed around a position at which an erect image (spatial image) of unity magnification corresponding to the aforementioned image is formed, and in which an aquatic plant, a rock and the like are placed near (in front of and behind) the formed image. In this example, an object (aquatic animal) like a fish is projected between the aquatic plant and the rock, whereby a virtual aquarium is reproduced (see PTL 2, for example).
However, the aforementioned formed image (spatial image) is projected directly in front of a microlens array in the aforementioned image display device. For appropriate viewing of this spatial image, it is necessary that a viewer, the microlens array and the image display surface are arranged in a straight line. This is disadvantageous in that it is difficult to obtain a three-dimensional effect, a sense of realism and the like.
On the other hand, the present applicant proposes a display device which includes a flat panel display such as an LCD, and a planar image-forming optical element (micromirror array, see PTL 3) including a multiplicity of recessed unit optical elements or protruding unit optical elements arranged in an array and each having two mirror surfaces (corner reflectors) orthogonal to each other in Japanese Patent Application No. 2012-249682, Japanese Patent Application No. 2012-259047, Japanese Patent Application No. 2012-283072 and the like.
As shown in FIG. 18, this display device is configured such that the flat panel display (referred to hereinafter as a display D) is disposed on a second surface side of (under) the image-forming optical element, with a display surface Da of the display D inclined at a predetermined angle α (not less than 30° and less than 90°) with respect to an element surface (P) of the image-forming optical element (micromirror array M). Thus, the display device is capable of sharply displaying a spatial image (I′) standing up obliquely toward the front side (viewer side) on a first surface side of the image-forming optical element (over the device) in a manner floating up from the upper surface of the image-forming optical element. In FIG. 18, a plane (frame indicated by dash-double-dot lines) designated by the reference character V represents a displayable range of the spatial image I′ (that is, “virtual display area” of the spatial image I′) projected from the display D.